The ICAN methodology (Instruction for the Calculation of Aircraft Noise) is based on geometrically defined flight paths and corridors and on grouped emission data of different aircraft types. Sources are 15 flight paths distributed in the defined corridors, ground movements on taxiways and APU-operations (Auxiliary Power Units) at parking positions. All aircraft types (propeller, jets, helicopters civil and militaire) are described by octave band spectra with directivity index for about 40 emission groups. The ground model can be described by points with defined ground height - this allows to calculate even runways with gradient in the vicinity of hilly terrain.

For the calculation the flight paths are segmented so detailed, that using smaller segments will not change the calculated results. These results are A-weighted equivalent sound pressure levels at fixed points or on grids presented as noise maps. They can be related to any time interval for day, evening and night. Mixed values like Ldn or Lden using corrections for some of these time intervals can also be evaluated. At defined receiver positions the distribution of maximal levels Lmax in intervals of 1 dB (or any other interval) can be determined.

Further the NAT(L) - this is the Number above threshold - for the user defined threshold level L can be calculated and presented at defined receiver positions or on a grid. This allows to define areas where the defined threshold level L is not exceeded more often than a defined number of times.